Telegraph distributor



Sept. 30, 1952 G. T. BAKER 2,612,562

TELEGRAPH DISTRIBUTOR l) JWM Seplt. 30, 1952 G, T, BAKER 2,612,562

TELEGRAPH DISTRIBUTOR Filed June 10. 1949 2 sHEETs--SHEET 2 @ffm/MVM ff 4MM Patented Sept. 30, v 1952 land, assgnor to British Telecommunications Research Limited, Taplow, Buckinghamshire,

- England, a Britishl company Application J une 10, 1949, Serial No. 98,193 In Great Britain June 14, 1948 (Cl. P18-'79) 12 Claims.

The present vinvention relates tocircuit arrangements for use in an electrical signalling system and is more particularly concerned with arrangements for dividing line time into a plurality of cyclically recurring equalelements to enable the transmission of an item of information during each element. l

A signalling system of this nature has many applications, for example, the remote transmission of different indications which may be continually varying or for the transmission of telegraph characters. The characteristic of the signalling system is that the items of information are available simultaneously and are transmitted successively by the division of line time.

In the case of telegraph transmission this has been done by means of a rotating contact arm or set of cams which is vcoupled by a clutch to a continuously-running motor. To maintain an accurate transmission speed in the face of the clutch impact and other variables, a fairly powerful motor is required ltogether with governor control. The amount of energy expendedl is therefore considerable and the mechanism is somewhat complex.

It is an object of the present invention to provide electronic arrangements for the division of line time and in particular to provide an electronic telegraph distributor operating on the start-stop principle. l

.According to one feature of the invention, a set of potentials representative of the information to be transmitted during each element Vof a cycle is simultaneously applied to a plurality of control circuits and serves tov determine whether pulses fed successively to said vcontrol circuits shall or shall not pass therethrough to effect the operation of a transmitting device which is arranged to transmit one signal in response to a pulse and to transmit a different signal in the absence of a pulse.v

According to a further feature of the invention, a cyclic electronic counter driven from a pulse source is arranged to feed pulses successively to a plurality of control circuits which are simultaneously conditioned according to the items of information to be transmitted during the elements of a cycle to absorb said pulses or to pass said pulses to a transmitting device which is arranged to transmit one signal in response to a pulse and to transmit a different signal in the absence of a pulse.

According to a further feature of the invention, a telegraph distributor comprises a source of pulses, means for feeding said pulses over one path to cause a transmitting device to transmit signals of one kind, meansffor feeding said pulses over a second path tocause said transmitting device to transmit signals of a different kind land anr electronic cyclic counter in" said second path for delivering pulses successively to a plurality of control circuits which lare simultaneously conditioned in accordance with the elements of a .character to be transmitted to absorb said pulses or'to pass said pulses to said transmitting device, the transmitting device being so arranged that the reception of a pulse y' over said second path nullifies the effect of the reception of the corresponding pulse over said first path. l I.

The invention will be better understood from the following description of one embodiment taken in conjunction with the accompanying drawings in which: v

Fig. 1 shows a schematic 'diagram of the arrangement and Figs. 2 and 3 whenl arranged with Fig. 2 on the left show the detailed circuits of the arrangement'.

The invention will be described in association with a teleprinter operating on the start-stop principle using a Ve-unit code. A perforated paper tape is fed through the teleprinter transmitting head which is provided with' selector contacts or feelers to sense the holes in the tape. The tape is advanced one step on the transmission of each character by known means controlled by a paper feed relay in the distributor. Double current working is assumed in which as is well known, positive corresponds to a mark and negative to a space. The start signal consists of a space having the same duration as an elementI of the character code while the stop signal consists of a mark having a longer duration.

Referring to Fig. 1 when no transmission is taking place the switch SW is in the open position shown. The pulse source which is shown as a multivibrator MV operates continuouslyy to feed pulses rover leads D and R but these pulses are ineffective in this condition of the circuit. The -multivibrator MV is very asymmetric, the ratio of the -tWo-non-conducting periods being of the order of 2000 to 1. In the present embodiment the duration of the two periods is approximately 20 milliseconds and l0 microseconds. The leads D and R are connected one to one valve anode and the other to the other, the arrange,- ment being such that short positive-going pulses are fed over lead D and negative-going pulses 3 of the same duration are fed over lead R. Lead D constitutes the drive lead to the scale-of-six cyclic counter C6 which is arranged to operate on negative-going pulses only while lead R, the reset lead, controls the stop toggle Z and the line toggle L. v Both theftoggle circuits are also arranged for operation' lby negative-going pulses so that it Will be understood that the cyclic counter will be operated by the trailing edge of. the pulses fed over lead D while the toggle cir- `cuits will be operated by the leading edges of the pulses fed over lead R, the trailingv and leading edges being separated by a period of ldmiczx-oseconds, the width of the pulses.. g l

When the switch SW .is closed, preferably automatically under the controL. for instance, of.y

the paper tape or by other suitable: means',I the next pulse over the reset lead R causes the trans- 4 control through the line toggle L the operation of the line relay to transmit the character corresponding to the perforations in the tape. The sixth pulse is fed to the stop toggle over lead 6 and causes the transposition of this toggle While the corresponding reset pulse. controls the line toggle to cause a.. mark to be transmitted over the line as a stop-signal. The transposition of the stop toggle causes over lead H the cyclic counter `to be again insensitive to pulses over the D' leadf although this control will be again lifted onthe. next. reset pulse if switch SW remains Closed.. The. next, reset pulse is delayed for a period which isA variable up to twice the duration of a single code element due to a control over lead AP which becomes elective when the stop ftoggl'e' is; transposed at the end of the transmission of a character.

position of the stop toggle Z which thereupon' transmits a negative-going pulse over lead SS to theA line toggle L. This .toggle is also. transposed'to change the marking condition on the line LI to a spacngcondition. thereby transmittingA a start signal over the line. K, .The.transposition Yof the. stop toggle. Z also causes. acontrolto be. exerted over the, hold..lead H. on the. cyclic counter, this control enabling the counter to, respond to pulses transmitted thereto over the. leadV D. However, the lead. H is associated, with delay means such that the con.- trol. does notbecome effective until after the negative-.going edge corresponding to. the nega .tive-going edge on. leadR... Hence the. first. pulse delivered by themvultivibrator is eiectiyeover lead R to cause the transmission of the start signal but is ineffective over lead. D on. the, cyclic counter..v l 4 Subsequent, pulses deliveredV over. lead. R tothe stop toggle Z are ineffective but. these-pulses. are also fed to the. line. toggle L and thev effect of the second pulse is to transpose the, line toggle to terminate the. start signal. Whether this transposition of the` line toggleis effective on the line relay depends on the first code element. of. the character tobe.- transmitted as. will.y nowY be explained. .l y

The cyclic counter CB, is arrangedto deliver an, impulse over each of thesix. leads l to4 6, in succession in response vto successive impulses from the multivibrator.. The rst impulse. to, be effective on thecQunter after the closing of the switchSW will be Ithe second. pulse. delivered over lead. D by the multivibrator and this pulse will be 10 microseconds behind the: secondpulse delivered over lead R. In response to this pulse, av negative-going pulse will be fed. over. lead l' to theappropriate one of the gate circuits G. Leads I to 5. from the cyclicY counter are connected to the4 gate circuits while lead 631s. connected to the stop toggle Z for a purposefto be described later. Five gate circuits are employed', each corresponding4 to oneV element inV the code, and are controlledbyY the ve selectorcontac-ts in the transmitting head. If the selector contacts are openthe gateV circuits are closed and the pulses from the cyclic counter do notv pass to theline toggle and vice versa. Assumingthat gate l is open, it will be understood that the pulse from lead I will arrive` at the line toggle a very short time (of the order of 10 microseconds)` after the pulse over`v the reset lead R. Hence before the line relay is able to respond following transposition due to the reset pulse, the toggle is again transposedy due to the pulse from the gate circuit. The'fi've pulses from the cyclic counter areffed successively to the five gatecircuits vto The above-described operation continues until the switch SW is opened and it will be noted that. the circuit.v can onlycome to rest in one. position,v that,v is whenv the. stop. signal has been transmitted.. Thev line. and stop. toggles, include relays for controlling the: line current and paper feed'` respectively.

A description will. now be `given of. the detailed circuits shown in Figs. 2 and. 3, commencing with the multivibrator MV. This is a. substantially conventional circuit but the values .of the. components in vthe cross. connections. between the anodes. and. grids, of the two. valves VT and. V8 are' such that the. ratio of meinen-conducting period of the. valve V8. tothe non-conducting, pe.- riod ofy the` valve.- VT is. of the order of 200.0 to.` L. the duration ci` manon-conducting. period. .ofi V1 and the conducting period; of. V8 being` approximately 1-0, microseconds 'whilethe conducting. period of` Vl and the. non-conducting period' of V8 is. approximately 2 0 milliseconds i. e., the. usual duration of one character element. Positivegoing 1,0I microsecond pulses are thus. delivered over lead D and negative-going pulses ci'y the same duration. are. delivered over lead R as previously explained. It will be noted thatv the charging resistance R9 for condenser C3 is. vari.- able to allow for the adjustment. of the abovementioned ratio and' the charging. voltage isv dorived' fromv the stop toggle Z'.. During trans-v mission this charging voltage is close to earth potential since valve V9 is non-conducting. but when the stop toggle is transposed on. the 6th impulse from the cyclic counter, V9 conducts and the chargingA voltage is consequently re.- duced. The duration of the non-conducting period of the valve V8 is thus increased to enable a long marking signal to be transmitted to. line, the increase iny the duration being adjustable by varying the position of' the tapping on the anode resistance R.

TheA cyclic counter C6 consists of three stages each consisting of a double triode although it will be understood that separate valves may be used if desired. The stage coupling e. g. via- CI and RI from Vlf to V41 and C2r and R2 from V4 to Vl, ensure that onlyA one valve of a, pair isA conducting at any one time, while the interstage coupling e. g. via R3 and R4' between stages l and 2, R5. and R6. between stages 2 and 3l and R7 and R8 between stages 3 and l, ensurethat assuming valves VI, V2y and V3 are conducting initially then the order in which the val-ves1 on- Y duct in response to successive input pulses isv V2,

In the initial condition when n0 transmission is taking place, valvesl V4, V5' and V6 are conl ducting. The component values of the circuit are sochosen that the grid potentials of V2 and V3 are 'approximately -25 volts but the grid potential of VI, being in part derived from the anode of V3 which isnon-conducting is about l5-volts. The 'input pulsesnare arranged to have an amplitude of approximately volts negative and are applied in common to the cathodes'.v A pulse of this amplitude will-be suflicient to cause VI to conduct whereupon the stage triggers' vand V4 becomesnon-conducting. VA negative-going pulse is fed from the `anode of `VI to leadv I.' Valves V5, V6 and VI are now conducting'wit-h valve V2 in the sensitive conditiondue to-its grid potential being derived inpart from the anode of V4 which is now 4non-conducting. In this manner successive input 'pulses' cause the transposition of the stages in the order n given aboveand a negative-going pulse is obtained from each anode as it becomes conducting, the `pulses being fed over leads I, 2, 3, 4, 5 and 6 in that order.v v I Leads I to 5 from the counter C6 are connected to the viive gate circuits GI to G5 (Fig. 3).", Each gate circuit includes 'a selector contact SCI tov SC5 together with a combination of linear and non-linear resistors. The operation of the gatecircuits are similar and thatfof GI only will be considered in detail. When the selector contacts SCI are open indicating'thata marking signal is to be transmitted to'line the point age approaches that of earth and the rectiiier MRB becomes non-conducting. The holdslead AI-I now has no effect on the counter and VIL betransmitted over lead Dnwhile the Z toggle is trig- .Y

gered bythe negative-going-leading edge lof the pulse transmitted over lead R and since these -two edges are separatediby 10 microseconds, a delay slightly greater :than this will be sufficient. When the valve V I0 becomes conducting on the transposition of the toggle Z, a negative-goingpulse is fed over leadv SS, C5 and RIB to the line toggle L. In thevnon-transmittingcon- X is at substantially earth potential and the rectierfMRBI will be non-conducting. On the reception of a pulse over lead I, the point X will go sharply negative,V the "rectifier Vwill conduct and the pulse will be shunted to earth overresistance RIS. When the contacts are closed, re` sistances RIB and RI5 form a potentiometer and their values are sojchosen that the potential at their junction point is approximately 1 20 volts. Hence point X can go 20 volts negative before any appreciable shunting action takes place.

Under these circumstances, the vpulse developed across`RI4 is fed via MRAI to the line toggle L, thefrectiers MRAI to MRA5 being provided to prevent any interaction between the gate circuits due to their common output.`

The stop toggle `circuit Z and the line toggle circuit L are similar and include a thermionic valve arrangement having two stable conditions of equilibrium. Referring first to the vstop toggle Z, when no transmissionv is taking place i. e.v a marking condition is on the line LI,A the valve V9 is conducting and VI'U is cut off. In this condition, as previously mentioned, a control is exerted over the lead I-I on the counter C6 ywhereby the latter is unresponsive to pulses fed over lead DL When describing the operation of the counter'l it was explained that valves V4, V5 and V6 are conducting when no transmission'is taking place while VI is the next to conduct. However, since the multivibrator is operatingrcontinuously, it 'is desirable that the counter should be unaffected by :pulses fed over leadDuntil the switch SW is closed and this control is eiected over lead H. Since V9 is conducting, its anode voltage will be considerably below earth potential, while the control grid potential of valve VI as. previously explained is at approximately f-'l5v'oltsL Under these conditions the rectier MRB conducts and theQpOtential at the control gridr of'VI falls to approximately -25 volts so that VI is :insensitive to pulses over the lead D. When the switch SW is closed, the stop toggle is transposed andVS becomes non-conducting so thatthev anode Volt'- diitnon, valve VI2 is' conducting vand valve-VII is non-conducting, while the polarised relay M is de-energised, the contact is in the position shown and a marking condiiton isvon the line LI. Whenthe negative-going pulse is' received over the lead SS, the linel toggleL is transposed and the relay M operates to transmit a spacing signal. This signal existsv'until the nextreset pulse is received over the lead R. This will cause the line tozzle L to krevert'toits original condition. However, the pulse transmitted over the lead D corresponding to this second reset pulse will cause ak negative pulse to' be transmitted over ,lead I; from the counter.` to the` gate circuit 'GL Assuming that the gate circuitv GI Vis open i. e. the selector contacts SCI are closed, the pulse will passthrough the gate circuit and Will be eii'ective on the valve VI'2 a short time after this'valve has been made conducting due to the second reset pulse on lead R.V The line toggle L is thus, again transposed before the relay M has hadtime to releasevand the spacing condiiton is retained for the first element of the character.

This condition will exist until the next reset pulse isreceived by the line vtoggle Which will be transposed tothe marking condiiton unless the `gate circuit vG2 is open when the operation Will again be as `describedabove and a space signal will be transmitted. The Icircuit continues to operate in this way until the ve signal elements have been transmitted. The seventh reset pulse which is transmitted at the end of the "fifth element ensures that the line toggle is in the marking condition since in this case there is no control via a gate-circuit. vFurther the sixth pulse from thecounting circuit is delivered to the control grid of VID of the stop toggle Z'. The stop toggle Z is thus transposed and V9y cOnducts thus reducing the charging voltage applied to condenser C3A in themultivibrator due to'the connection via AP, therebydelaying the transmission 'of the next reset pulse'to give a long stop signal. This reset' pulse will beapplied to the stop toggle Z and serves toftranspose the toggle to transmita pulsev over lead SS as previously described thereby intitiating the transmission of the next character. It should be noted that the stop toggle Z includes a polarised relay P which is energized onjth'e initial vtransposition of the stop toggle and is released cnthez second transpositionat the endl of the trai'ismission of the character inl order tdstep on.' tl'i tapeiin, readiness. for the.- transmission of the next character. :f l

It .will be 'understood that various modifications: may be made in: the circuit. For instance, thepu'lses deliveredby the counter may be arf ranged. toy bey coincident with the -resetpulses but ofr considerably;'greaterv amplitude th-an the reset pulses so thatthefreset pulses are over- Whelmed. The coincidenceV between reset `and drive pulses wouldjbe. obtained by using one output .of the multivibrator for the two series of pulses. .Y z j r 'i lFurther the gate circuits. may be modified so that onlya single rectier isnecessary. Thus the lead,y for instance,..lead l, from the cyclic counterrvvill extend to the gatecircuit. via-a condenser to one pole of ythe rectifier which will correspondto MRAI of Fig..'3;. An. earthedresistorf and an earthed capacitor `will be connected tog-the: lead between` the condenserv andv rectier and 'between these two vconnections will beccnnected the pecker contacts.v Then Vvifthevpeclrer contact is closed to -connect direct earthto the lead,vthe gatefcircuit is'closedyand a mark is transmitted toline While if the ypecker contacts -are open, the gate will be openand a space will be:transmitted..y yw. I, v v

It will be understood-,1 ofcourse', that the -distributor may beused with an automatic transmitting head asdescribedabove or with a `keyboard operated machine. In-this 'case`r operation of any 'key aswell as controlling the.; operation ot one or more of iive'code bars also controis the 'operation' of a sixth bary which =has for effect the closingicf the switch SW to initiate transmission'.` The code bai'swill, of course, control contacts similar to the pe'cler contacts; while'in raddition theoperation 'of relayv Pwill serve to' lock the operated' code 'bars-i until'A trans; missionhas been completed.` .'Iclaim: 1'.,In a telegraph distributor,. ajpulsesource', a vtransmitting device;vmeansjfoi 'ieeding `*pulses from said sourcefoveii one .pathgto said transvvInitting' device, means for feeding pulses from said source over a second` path to said r"trans-L mitting device, a plurality'gof control' circuits associated with said second rpath,y meansjior simultaneously conditioningv said .control circuits in accordance with the elementsof a character Ato be transmitted, an electronic counter included 'ii saidsecond path for d'eliveringjsaifd pulsessuc'- c 'essivelyto said.controljcircutsand means lin said' control circuits forldetermining in dependence'uponlthe conditi-0n'. thereof which vof said successive pulses arev to pass .therethrough `by said; transmitting `device toename saidjtrans. mitting device to be'iniiuenced solely by pulses ifedf'over one'path to transmitione kind of signal and jointlyvby pulsesl fed overv both paths to transmit. another kind of signals.

Ylin electrical signalling system, al' circuitarrangement for dividing line time into va plurality 'of cyclically vrecurring. equal elements to enable 'thetransmission of. an itemv of im formation during each element comprising a plurality of gatefcircuits, means forfeedingpulses successively. t said gate circuits, mechanically operated means .vfor simultaneously applying to saidgate circuits a setY of` potentials represent-r ing'items of information to control the opening 3nd,.;closingof said gate circuits and'transmit:

ting. means.; opera-ted fby the pulses vpassing throughv the cpenfgate circuits. 1 l 3. Ina telegraph distributor, a-pulse source, a transmittingidevice, means for-transmitting resetv pulses; over one path to control the. oper-a.- tion of :sa-id Itransmittingdevice vin one sense, means fork transmitting drive pulsesvoverfasecond- .pa-thV to Vcontrolthc operation of .said transmitting device, in a differentv sense means in said second f path for g-roupingffsaid drive pulses into cycles, `tape controlled.; selector contacts, .associated. witnsaid secondi path, means alsoin said;s econd-patlrforz absorbingA selected drive impulses;l :inf-,a y cycle 'as determined. by*l said selector contacts yand means .in said transmitting device vforgenablingit-"to operate in said differentisense in' response toysimultaneously .applied drivef and reset pulses. .j

4..;-In a telegraph distributor,a .pulse source, acline toggle circuit-a transmitting relay con.-y trolledf thereby', means for transmitting vreset pulses over one path to control the operationnof said. line toggle; circuit in one sense,y to i,clause said transmitting s` relay .'60 transmit ...a gmark, means for.transmitting` drive` pulsesV over aj sec.: ond pathfto control` thefoperationiof-'said line toggle circuit" in a-jdiierent sense to cause said transmitting relay to transmit a space,l a-cyclic electronic counter insaid..r second;y path,r tapecontrolled vselector contactsvfassociated `witlfr said second path,-means alsoY infsaid; second-path for absorbing selected driveimpulsesin acyclegans determined by saidjselectorccntacts:and means in-,said line toggle circuit for enabling said-transy mitti-ng relay to transmital space in response .to driveiandresetl pulses simultaneously appliedto said-line toggle circuit. r if v5, Ar'telegraph transmitter'as claimedin claim 4- wherein means are provided for ensuring that the drive pulses applied-to said lineI toggle circuit 6. A telegraph transmitter as claimed inclaim` 4' wherein means are Y.provided for delaying-.the

application cfthe drive pulsesto saidl-inetcggle circuit With'Vrespect-,tdsaid resetgpulses.'

7. In a telegraph distributon-a-multivibrator circuitta transmitting device, means for transmitting reset pulses from said multivibrator cire cuit overv One path-to control .i the operationfof said xtra'nsI-iiitting device in one sense, means for. transmitting drivepulses frcm-said multivibrator circuity overa second path to control the opera.- tion of said transmitting device .ina different sense, lmeansf'in said second path for grouping said drive pulses into cycles, yselecting means associated withasaidV second path, means also in said second path- :for absorbing selected drive pulses-in acycle as determined by said selecting means and Vmeans infsaid transmitting'device forI enablingi-t/tol operate in said diierent sense in response to; simultaneously. applied drive and re.- set pulses. ""8; A telegraph vdistributor'as claimed in claim' 'fwheren said multivibrator circuitis asymev metric andxme'ans are' provided for deriving the reset pulses from the negative=going edge of one anode waveform an'dfthev drive pulses from the negative-going edgewof the other waveforml whereby said drivepulses` arel delayedA with re'- spect to said reset pulses.

9;"A telegraph-distributor as claimed in'claim IT'rwl'iereinY said'.multivibrator circuit is asym-` metricV andmeans are provided for deriving the ,drive and-reset -pulses from the*negative-going edge of one of said anode waveforms whereby said pulses are coincident.

10. In a start-stop telegraph distributor employing a code having a fixed number of elements, a line, a multivibrator, a stop toggle circuit, a transmitting device, means in said stop toggle circuit responsive to a pulse transmitted thereto from said multivibrator for changing over said stop toggle circuit, means responsive to the changeover of said stop toggle circuit for controlling said transmitting device to transmit a start signal over said line and for enabling subsequent pulses from said multivibrator circuit to control said transmitting device to transmit over said line marking and spacing signals corresponding to the elements of the code, means in said stop toggle circuit responsive to a pulse transmitted thereto subsequent to the pulse corresponding to the last element of the code for changing over said stop toggle circuit, means in said transmitting device for responding to said second changeover of said stop toggle circuit for transmitting a. stop signal over said line and means responsive to said second changeover of said stop toggle circuit for delaying the generation of the next pulse by said multivibrator in order to lengthen said stop signal.

11.`A telegraph distributor as claimed in claim wherein said second changeover of said stop toggle circuit reduces the charging voltage applied to said multivibrator circuit.

12. In a telegraph distributor, a multivibrator circuit a cyclic electronic counterhaving a scale greater by one than the number of elements in the code employed, a plurality of gate circuits one for each element of the code, tape-controlled selector contacts for opening said gate circuits, a stop toggle circuit, a line toggle circuit, control connections from said stop toggle circuit and from said gate circuits to said line toggle circuit, a transmitting device controlled by said line toggle circuit, means for feeding pulses from said multivibrator circuit to said electronic counter and to said line and stop toggle circuits, switching means in said stop toggle circuit for preventing said pulses being eiective until after the operation thereof, means for applying the first pulse after the operation of said switching means to said line and stop toggle circuits only to effect change-over of said stop toggle circuit and line toggle whereby said transmitting device is caused to transmit a start signal, means for rendering subsequent pulses in the cycle effective on said electronic counter and said line toggle circuit, the successive pulses delivered from said electronic counter being fed through the open ones of said gate circuits to said line toggle circuit in opposition to the pulses fed directly thereto, means for causing said linev toggle circuit to respond to the pulses fed thereto from said gate circuits when pulses over both paths are present whereby said transmitting device is caused to transmit a spacing signal, means for causing said line toggle circuit to respond to the pulses fed directly thereto whereby said transmitting device is caused to transmit a marking signal, means for feeding the last pulse of the cycle delivered by said electronic counter to said stop toggle circuit to changeover said stop toggle circuit and said line toggle circuit whereby said transmitting device is caused to transmit a stop signal and means in said stop toggle circuit for delaying the nextpulse delivered by said multivibrator circuit in order to lengthen the duration of said stop signal.

GEORGE THOMAS BAKER.

REFERENCES CITED UNITED STATES -PATENTS Name Date Rea Apr. 26, 1949 Number 

